The Wireless Telegraph 



other subscribers, whose wires are often far away 

 from our own. 



The first practical use of induced currents in 

 telegraphy was when Mr. Edison, in 1885, enabled 

 the trains on a line of the Staten Island Railroad 

 to be kept in constant communication with a 

 telegraphic wire, suspended in the ordinary way 

 beside the track. The roof of a car was of in- 

 sulated metal, and every tap of an operator's 

 key within the walls electrified the roof just long 

 enough to induce a brief pulse through the tele- 

 graphic circuit. In sending a message to the 

 car this wire was, moment by moment, electrified, 

 inducing a response first in the car roof, and next 

 in the " sounder " beneath it. This remarkable 

 apparatus, afterward used on the Lehigh Valley 

 Railroad, was discontinued from lack of com- 

 mercial support, although it would seem to be 

 advantageous to maintain such a service on other 

 than commercial grounds. In case of chance 

 obstructions on the track, or other peril, to be 

 able to communicate at any moment with a 

 train as it speeds along might mean safety in- 

 stead of disaster. The chief item in the cost of 

 this system is the large outlay for a special tele 

 graphic wire. 



The next electrician to employ induced cur- 

 rents in telegraphy was Mr. (now Sir) William 

 H. Preece, the engineer then at the head of the 

 British telegraph system. Let one example of 

 his work be cited. In 1896 a cable was laid be- 

 tween Lavernock, near Cardiff, on the Bristol 

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